1. Technical field
The present invention relates to an apparatus and method for manufacturing an automotive beam and in particular to an apparatus and method for roll forming a closed profile beam.
2. Description of the Background Art
Beams used on the body structure of an automobile and beams mounted at the front and rear of automobiles are required to absorb impact from collisions with other vehicles and with other objects. Beams manufactured for these purposes need to have a high resistance to torsion and good strength characteristics in order to prevent local buckling of the beam. A number of prior art patent and patent application specifications have disclosed beams for use in the automotive industry and apparatuses and methods for manufacturing such beams.
U.S. Pat. No. 5,934,544 provides an apparatus and method for manufacturing automotive bumper beams by a single roll forming process. The apparatus includes an uncoiler, a straightner, a group of roll formers, a sweep roll former, a welding member and a cutting member. The method of manufacturing the bumper beam includes preparing the sheet metal, forming the cross sectional profile, forming a sweep, adjusting the tubular cross sectional shape of the sheet metal and welding the sheet metal prior to cutting the beam into desired lengths. The objects of the invention are to provide a beam with strengthened impact resistance, reduced weight and to simplify the manufacturing processes of the prior art.
WO 97/30882 (International Patent Application No. PCT/SE97/00305) discloses a vehicle body comprising a beam structure consisting of thin-walled flange-free profile parts with closed cross sections made by means of roll forming. The component parts of the beam structure are hardened so that the boron steel or other high tensile steel has a yield limit of the order of 900–1100 MPa. The object of the invention is to produce a new and lighter type of vehicle body with an increased body strength and stiffness.
In order to maintain an efficient manufacturing process for beams, it is important to use a production line technique manufacturing beams in a relatively small number of steps while maintaining their structural integrity and safety characteristics. The safety and structural integrity aspects are particularly important when the beams are manufactured for use as protective members in an automobile. Although the techniques disclosed in the above referenced specifications maintain an efficient manufacturing process and address the issues of improved strength characteristics and weight of the beam, significant improvements could still be made regarding the safety aspects of beams for use in automobiles which would inevitably result in improvements to human safety.